Electronic measurement equipment is typically operated with one or more probes. The function of each probe is to conduct a signal from a circuit under test to the measurement equipment where the signal is displayed or processed. Each probe typically includes a conductor for transporting the measured signal and another conductor which is tied to ground. In addition, a probe can include circuitry which amplifies or attenuates the amplitude of the measured signal in a uniform manner. One characteristic of a probe is its ability to accurately deliver a signal lying within some range of frequencies in the circuit under test or an amplified or attenuated replica thereof to the measurement equipment. One part of this characteristic, referred to as the frequency response of the probe, is defined as the variation of the ratio of the measured signal amplitude to that delivered to the measurement equipment with frequency. For accurate measurements, the frequency response should be unity or some constant value for some range of frequencies which encompasses the frequency of any measured signal.
Equipment which provides different types of electronic measurements is designed with the ability to provide accurate measurement of a signal amplitude in a circuit under test extending over a predefined frequency range. In general, the greater this frequency range, the more expensive the measurement equipment. While amplitude measurements of test signals having frequencies lying outside of this predefined frequency range may or may not be possible, depending on the measurement equipment, any results may be grossly inaccurate. For example, significant overshoot and ringing can be displayed on an oscilloscope which can easily be interpreted as noise in the circuit under test.
It would be extremely desirable if the frequency range or bandwidth over which accuracy amplitude measurements can be made with a given piece of measurement apparatus could be expanded. Such expansion would increase the capabilities of any piece of measurement equipment and could avoid the need for additional measurement and test equipment purchases.